As the name suggests, Open Packet DWDM is essentially an open-source version of packet-optical technology for metro and long-haul fiber optic transport networks – it decouples software and hardware, and uses open specs that anyone can use to contribute their own packet-optical systems, components or software.

Voyager is a new DWDM transponder platform based on those specs. Developed in conjunction with Acacia Communications, Broadcom, Celestica, Lumentum, Snaproute and Coriant, Voyager leverages data center technologies that Facebook implemented in its Wedge 100 top-of-rack switch. To the engineering blog post:

In the beginning, the open line system will include Yang software data models of each component in the system, and an open northbound software interface (NETCONF, Thrift, etc.) to the control plane software. This allows multiple applications to run on top of the open software layer, enabling software innovations in DWDM system control algorithms and network management systems.

Figure 1: The open line system architecture

We have extended the system in Figure 1 all the way to the transponder — the hardware component at the ends of the open line system (ends of the arrows in Figure 1). The transponder takes in client data signals (e.g., 100 GbE) from switches or routers, and packages these signals into the proper signaling format for metro or long-haul transmission.

The DWDM transponder hardware includes DSP ASICs and complex optoelectronic components, and thus accounts for much of the cost of the system. These components are a maturing technology, with recent advancements mainly in integrating functions to drive down the power, size, and cost. The software that runs the transponder is traditionally bundled with the hardware, and innovation happens only at the system level. By opening up the transponder, Voyager will enable greater innovation at the component level.

Facebook said that Equinix has successfully tested Voyager and Lumentum’s open line system over 140km of production fiber. South African telco MTN has tested Voyager over its production fiber network. And ADVA Optical Networking has already pledged commercial support to market Voyager and provide network management, operations support and maintenance.

As for the obvious question – why is Facebook fooling around with DWDM? – the answer is that Facebook’s TIP projects up to now have focused mainly on wireless broadband access, such as its Aries massive MIMO tower, OpenCellular 2/3/4G base station and Terragraph small cells solution, as well as unconventional technologies like UAVs delivering connectivity.

But all of that requires backhaul, and the vast scale of connectivity that Facebook wants to enable – and the deluge of internet traffic that will result from connecting more people, most of it driven by video and (eventually) virtual reality – means that backhaul infrastructure will have to be scalable and cost-effective enough to support it. And while Aries is designed as a backhaul solution, at the end of the day, Facebook says, “The highest-performing bandwidth and reach technologies are still fiber-based — particularly switching, routing, and transport DWDM technologies.”

… the pace of [DWDM] innovation has slowed over the past 10 years as we approach the limits of spectral efficiency. We believe that this presents a great opportunity to adopt an open approach that will drive greater efficiencies in DWDM transport. By unbundling the hardware and software in existing “black box” systems, which include transponders, filters, line systems, and control and management software, we can advance each component independently and deliver even more bandwidth with greater cost efficiency.

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